A high-energy beta (beta-) emission and short half life (16.9 hr) makes 188Re an excellent isotope for radiotherapeutic applications. The similarity in the chemical behavior of Re and Tc means that imaging [protocols developed for 99mTc can be directly converted to therapeutic protocols for 188Re. Unfortunately the short half-life that makes Re attractive as a therapeutic agent makes it impossible to supply from a central source. Current generators are not adequate for the reliable delivery of pure 188Re at the end user site. The aim of this project is to develop a superior generator system for 188Re with an increased operating life to reduce the cost and improve the availability of the radioisotope to end-users. Crystalline inorganic compounds under consideration are layered aluminum mixed hydroxides, which can be synthesized as anion exchangers. The ideal compound strongly retains divalent tungstate (WO4 =) but not monovalent perrhenate (ReO4-). After testing a range of compositions for both magnesium and lithium aluminates compositions were entitled with high tungstate retentions (Kd >1.8 . 10[6] for Mg and >8 . 10[4] for Li). Based on equilibrium tests, these compositions had WO4=/ReO4 - separation factors of 18,000 and 500 respectively. The compositions were pelletized (<300 mu m) and used to produce small generators, which were tested and found to reliably deliver 188Re completely free of 188W, demonstrating separation factors greater than those seen in the equilibration tests. Phase II of this project will include improved pelletization and exchange kinetics for the ion exchangers and will culminate in the fabrication and testing of full size generators based on this technology. The ultimate goal of this project is a commercially viable 188Re generator for use in end use facilities such as hospitals, radiopharmacies, and regional radiopharmacies serving multiple hospitals. This will improve the availability of 188Re for use as the active component for radioimmunotherapy (RIT) and similar techniques.